"Your practice of inducing users to violate their contractual agreement with YouTube constitutes a tortious interference of a business relationship."

-- From a cease-and-desist letter sent by attorneys for YouTube, a video-sharing site whose huge popularity stems largely from being a repository for copyrighted material, to TechCrunch blogger Michael Arrington, accusing him of copyright infringement.

Arrington, who created software that allows users to save YouTube videos to their hard drives, pulls the offending app from his site.